Notch signaling plays a critical role in the initiation and progression of various malignancies, and has been targeted therapeutically for several malignancies in clinical trials. Despite the consensus that Notch signaling is deregulated during prostate carcinogenesis, Notch has not yet been employed as a therapeutic target for prostate cancer due to the inadequately defined role of Notch signaling during prostate cancer progression. Our preliminary studies showed that increased expression of the active Notch1 intracellular domain (NICD) in the prostate (the PB-NICD model) promotes prostate luminal epithelial cell proliferation, supporting Notch as a pro-oncogenic pathway in the prostate in vivo. In addition, most Notch signaling components are upregulated in prostate tumor specimens of patients that developed recurrent metastatic diseases. Consistent with this observation, our preliminary studies show that increased Notch activity induces anoikis resistance of prostate epithelial cells and enhances the in vitro and in vivo metastatic potential of prostate cancer cell. Based on these preliminary studies, Notch signaling may promote prostate cancer metastasis. The goals of this application are to determine how Notch signaling alters prostate epithelial cell biology, and to determine whether and how Notch promotes prostate cancer metastasis. To achieve our goals, we will increase Notch activity by manipulating either Notch ligand or receptor in mouse models for human prostate cancer to directly determine whether Notch signaling promotes prostate cancer metastasis. In addition, a combination of genetic, molecular, and cellular biological approaches will be utilized to investigate the molecular mechanisms through which Notch promotes anoikis resistance. Finally, we will perform high-throughput screenings to identify small- molecule compounds that suppress Notch induced anoikis resistance.